Railroad hopper cars are commonly used to transport materials or commodity between distance locations. Railroad hopper cars typically include an underframe for supporting a walled enclosure or hopper in which the materials are held and transported. As is conventional, the underframe of the railcar is supported toward opposite ends by well known wheeled trucks which ride on rails or tracks. A bottom of the walled enclosure or hopper is typically provided with two or more individual discharge openings for allowing the material or commodity to be discharged from the hopper. The hopper on the railcar furthermore typically includes sloped or slanted walls or sheets angularly extending downward toward each discharge opening to promote gravitational movement of the material in the hopper toward the discharge opening.
In the prior art, a combination gravity and pneumatic discharge gate assembly is arranged in registry with each discharge opening on the hopper to selectively control the discharge of material from the hopper of the railcar either by gravity or pressure differential such as vacuum. Such a discharge gate assembly typically includes a frame defining a discharge opening and a first element or gate slidably carried by the frame for movement between closed and open positions. A combination gravity and pneumatic discharge gate also includes a pan assembly or second element, carried by the frame for sliding movement between closed and open positions and beneath the first element or gate.
Most gate assemblies also include a drive mechanism for operably moving the gate between the closed and open positions. When in an open position, the gate allows the material or commodity to gravitationally pass and be discharged from the hopper car. If the gate assembly is to be used for gravitational unloading of the material from the hopper car, the pan assembly or sanitary door must be opened first followed by the gate.
In the event pneumatic discharge of material from the hopper is desired, the gate is first opened to allow material to flow toward the pan assembly or second element. Typically, the pan assembly defines an open ended tube through which material is discharged from the hopper car. A selectively closed cap is provided toward the discharge end of the tube. In some embodiments, the pan assembly is fastened to the walled enclosure or hopper as with a plurality of fasteners. As will be appreciated, however, valuable time is consumed and lost by having to remove the pan assembly from the hopper car when the a gravitational mode of unloading the commodity from the car is selected. Arranging the pan assembly beneath or under the gate also reduces the clearance between the bottom of the gate assembly and the railbed over which the car travels between locations. As will be appreciated by those skilled in the art, the degree of clearance between the underside of the gate assembly and the railbed over which the railcar moves or travels is a serious concern when designing discharge gate assemblies for hopper cars coupled with customer pressures to increase the volumetric payload of each railcar.
Slidably mounting a pan assembly or second element on the gate assembly frame beneath the gate introduces significant design challenges. First, slidably mounting a pan assembly beneath the gate requires a second drive mechanism for moving the pan assembly between closed and open positions. As will be appreciated, providing a second drive mechanism for slidably moving the pan assembly or second element between closed and open positions complicates the design of the gate assembly in several respects. First, spatial requirements for the gate assembly, especially when considering the need for first and second separate and independent drive mechanisms for the first and second elements of the gate assembly, is limited. Second, providing a second drive mechanism on the frame of the gate assembly for sliding the pan assembly or second element between closed and open positions can adversely affect the clearance required between the gate assembly and the railbed. Of course, if the gate assembly is not properly spaced from the railbed, significant damages can occur as the railcar moves between locations. Simply raising the gate assembly, however, reduces the potential volumetric payload or capacity of the car while also raising the railcar's center of gravity Third, the addition of a second drive mechanism complicates the direction which each drive mechanism is to be turned or rotated to effect movement of the particular element on the gate assembly. Moreover, adding another sliding element to the gate assembly requires additional structure for inhibiting inadvertent movements of that second element from the closed position during railcar impacts which are a common occurrence in the railyards as the railcars are connected to each other during the formation of the train consist.
Another concern involving the design and engineering of a railroad hopper car gate assembly relates to the ability to maintain an underside of the gate protected against foreign matter, accumulation of moisture, or insect infiltration. In this regard, some railroad hopper car discharge gate assemblies include a flanged skirt arranged in surrounding relation relative to and in depending relation relative to the discharge opening defined by the frame of the gate assembly. The flanged skirt defines a discharge plenum. Typically an air sled or other form of unloading device is clamped or otherwise releasably secured to a lower flange on the skirt during a gravitational discharge of material.
To inhibit debris, insects and moisture, and other forms of debris from contaminating the underside of the gate and interior of the discharge plenum during transport of the hopper car between locations, such gate assemblies include a sanitary plate or cover element positioned beneath the gate to close the discharge plenum and protect the underside of the gate. Known sanitary plates or cover elements are neither designed nor configured to withstand the columnar load which can be placed thereon by the materials within the hopper and after the gate is moved toward an open position.
As mentioned above, in a railyard during make-up of the train consist and as they travel between locations, railcars can be subjected to numerous impacts, some of which can be severe. For example, when a railroad hopper car moves down a hump in a classification yard, it will impact with other railcars on the track ahead of it and such impacts can be forceful—especially when the railcars are filled with commodity or materials. While shock absorbers are typically built into the coupling units at opposed ends of each railcar, significant impact force are realized between two colliding cars. Such impacts and shocks can affect the position of either gate assembly element, i.e., the sliding gate and/or the second element or pan assembly, due to the inertia of either or both elements.
Accordingly, the gate assembly design can be further complicated by the need for a lock for inhibiting the sliding gate from inadvertently moving from the closed position toward the open position. As will be appreciated, if the gate moves from the closed position toward the open position—even slightly—material within the hopper can be inadvertently lost during transport of the railcar between locations resulting in an economic loss. When the gate assembly embodies a movable pan assembly or second element disposed beneath the gate whereby limiting contamination of the underside of the gate and discharge plenum, the gate assembly design is furthermore complicated by requiring still another lock for inhibiting inadvertent movement of the pan assembly or second element toward the open position from the closed position.
As such, each gate assembly on the railcar is typically provided with some form of locking mechanism for releasably maintaining the gate in a the closed position. The heretofore known locking mechanisms for maintaining the gate in a closed position have a myriad of different designs. Basically, however, such locking mechanisms include some form of mechanical lock which requires manual operation to move the lock from a locked condition to an unlocked condition and then back to a locked condition after the gate is returned to a closed position. Besides adding to the complexity of the gate assembly design, the addition of a second element, which is preferably maintained in a releasably closed position as the railcar moves between locations, also adds to the complexity of the lock assembly design.
For several reasons, the heretofore known manually operated lock mechanisms are constantly being destroyed when the gates are moved from their closed position toward an open position. Typically, and when the railcar arrives at an unloading site, an automatically operated driver engages with the drive mechanism on the gate assembly to move the gate from the closed toward the open position with significant speed. As such, and when the railcar reaches the unloading site, the operating condition of the lock assembly is often overlooked. Alternatively, the manually operated locking mechanisms are initially opened prior to the railcar reaching the ultimate unloading station. Between the time the lock mechanism is initially opened and the time the railcar reaches the unloading station, the railcar may impact with other railcars once or several timers. Occasionally, such shock loads imparted to the railcars can return the locking mechanism to a closed or locked condition. Limited visual access, inconvenient physical access, human error and the increasing demand to unload the railcars as quickly as possible, all contribute to the manually operated locking mechanisms being either substantially damaged or completely destroyed. Also, the high-powered torque drivers used to move the gate from the closed position toward the open position can result in destruction of the locking mechanism. Adding a second manually operated locking mechanism for inhibiting movement of a second element from the closed position only further complicates the gate assembly design.
The American Association of Railways (“AAR”) has promulgated regulations dealing with or addressing gravity discharge gate assemblies in operation. The AAR Standard S-233 relates to issues involving hopper railway car outlet discharge gates, installation, the level of forces sustainable by the locking mechanism prior to inadvertent opening, lock operation, seals and a myriad of related gate assembly matters.
As mentioned, railroad hopper cars are used to transport tons of commodity or materials between distance locations. Accordingly, and although there may be multiple discharge gate assemblies arranged on a hopper car, the gate or door of each gate assembly is subjected to extreme columnar loading conditions. Besides being subjected to extreme columnar loading conditions, the materials being transported may be a relatively fine granular material, i.e., cement or the like. Residue of such fine granular materials tends to pass about and around the edges of the door or gate. When subjected to moisture during the course of travel of the railcar, such residue material, when combined with the moisture, can cause significant problems involving sliding the gate from the closed position toward the open position at the discharge station.
Due to the extreme columnar loading conditions on the gate particularly when coupled with the residue material interfering with operation of the gate assembly, a substantially high level of torque is required to be applied to the drive mechanism to move the gate from the closed position toward the open position. The level of torque is such that at least a portion of the drive mechanism is sometimes physically displaced from its normal fixed axis of rotation during the initial opening movements of the gate under the influence of such torque levels. Displacements of the drive mechanism can and often does adversely affect performance and timing of the gate assembly thus resulting in significant operational problems.
Thus, there is a need and continuing desire for a railroad hopper car discharge gate assembly including two elements each movable between a closed and open position and a locking mechanism that addresses and satisfies the drawbacks associated with the known prior art devices.